Crystal Engineering-Based Approach to Introduce Mechanical Compliance in a Series of Highly Luminescent Substituted Distyrylbenzenes

Mechanically compliant adaptive molecular crystals have recently attracted considerable attention because of their distinctive properties and potential applications across various fields. Nonetheless, the fundamental understanding and practical use of these materials are in the early stages of development. Integrating such mechanical compliance, such as flexibility and self-healing properties, into functional organic crystals is a promising area of research that can enhance their practical applications and durability in optoelectronics, sensors, and other technologies. This study presents a comprehensive analysis of the mechanical and photophysical properties of cyano-substituted distyrylbenzene derivatives, specifically, α-PDN-1, α-PDN-2, α-PDN-3, and polymorphic α-PDN-4. These compounds are characterized by their unique “twist elasticity,” resulting from changes in torsional coordinates due to substituent effects. While isostructural α-PDN-1, α-PDN-2, and α-PDN-3 exhibit a brittle nature, the α-PDN-4 polymorph stands out due to its mechanical compliance. Our structure and mechano-optical investigation reveal that the isostructural compounds maintain similar conformational rigidity and packing arrangements, leading to brittle mechanical behavior. In contrast, α-PDN-4’s distinct structural and mechanical properties highlight the influence of substituents on molecular packing and mechanical compliance. This study underscores the potential of cyano-substituted distyrylbenzenes in the development of mechanically adaptive optical materials, paving the way for future applications in flexible optoelectronic devices.